1. Field of the Invention
The present invention relates generally to the field of radar sensors and more particularly to high speed high resolution wide range and low power analog correlators and radar sensors that incorporate the same.
2. Description of Related Art
Conventional radar sensors are widely used in detecting the positions of one or more targets. These conventional radar sensors may have various detection range capabilities. Generally, the detection range of high resolution radar sensors may be shorter than the detection range of low resolution radar sensors. Due to many design constraints, it may be difficult and/or cost inefficient for conventional radar sensors to achieve a high resolution and a high detection range at the same time.
For example, attempts have been made in using wideband signals to improve the resolution of the conventional radar sensors. However, these wideband signals typically have high thermal noise levels when compared to narrow band signals, which may be used in conventional radar sensors with low resolution. The high thermal noise levels lead to the deterioration of the signal-to-noise ratio (SNR) of the receivers of the conventional radar sensors. Due to this SNR deterioration, the conventional radar sensors may have difficulties in receiving the wideband signals reflected by remote targets. Consequently, these conventional radar sensors may suffer from a decline in dynamic range. Because the dynamic range represents a ratio between the power level of the strongest received signal and the power level of the weakest received signal, the decline of the dynamic range will diminish the gap between the maximum detectable distance and the minimum detectable distance of the conventional radar sensors. As this gap is diminished, the detection range of these conventional radar sensors will be reduced accordingly.
To address this SNR deterioration issues, another attempt has been made in deploying high signal-to-noise ratio (SNR) analog-to-digital converters (ADCs) to improve the dynamic range and the detection range of the receivers of the conventional radar sensors. These high SNR ADCs typically have a large number of bits when compared to the ADCs having a low SNR. In order to maintain a high resolution, these high SNR ADCs samples reception signal at a relatively high frequency. However, because of the large number of bits and the high sampling frequency, the power consumption of these radar sensors can be prohibitively high and thus render the implementation of these radar sensors impractical.
To resolve this power consumption issue, yet another attempt has been made in deploying conventional analog correlators to lower the sampling rate of the high SNR ADCs. However, these conventional multiplier-type analog correlators may have a relatively slow detection speed. This slow detection speed can substantially hamper the performance of these radar sensors because the detection time of these conventional analog correlators can be very long. As such, these radar sensors may be incapable of detecting fast moving targets. This deficiency may render the radar sensors unsuitable for use in many military and/or commercial applications that involve detecting fast moving targets. Utilizing a conventional matched filter correlator is also not practical as the circuit required becomes too large when the PCR code is long. Furthermore, a conventional matched filter correlator is not flexible for code late and sequence patterns. For these reasons, in balancing the advantages and disadvantages, the conventional multiplier-type analog correlators are currently preferable.
However, there remains a need for an economical radar sensor with high speed, high resolution, wide range and low power consumption.